What did concentration camps look like?

There are no verifiable pictures to indicate the exact conditions that existed inside retainment camps, as the Allies destroyed literally tons of documents and other evidence in order to shape public opinion in support of the Allied invasion. Most likely, there would have been several buildings which housed inmates. There likely would have been other facilities in which inmates worked on various projects. There has been no verifiable data or evidence to indicate that any gas chambers existed or were used for mass extermination. This is why I hesitate to use the words "concentration camp" as this tends to indicate a death camp; but however, evidence seems to suggest that the Germans had retainment camps, not death camps, just like the U.S. also had during the war to retain Japanese Americans of the time.

Another view

There is ample evidence, anecdotal, documented and eyewitness to show the condition that existed in the camps. The name people use for these camps reflects what happened in them. The name given to them by those that ordered them built and who subsequently managed them was the propaganda.

Most concentration camps were from Old Military barracks. So an average concentration camps would look like a Military base but with Gas Chambers, Piles or Pit full of dead bodies.